The rapid pace of recent technological development has been made possible by improvements in microfabrication techniques. One technology that has fueled the development of microfabrication for semiconductor processing as well as other manufacturing fields is photolithography. In a typical positive photolithographic process, a mask is first placed over a silicon wafer which has been coated with a resist. The resist is then exposed to light through the mask, rendering the exposed sections of the resist non-adherent to the silicon wafer. Finally, the exposed resist is rinsed away to reveal the silicon substrate. In a negative photolithographic process, the non-exposed portions of the resist are removed. The substrate can then be processed, for example, by etching or plating, producing a pattern on the surface. However, one drawback to this process is that the initial lithographic process is limited to line-of-sight applications. In addition, traditional lithographic techniques require the use of large quantities of liquid etchants that are difficult to recycle and dangerous to dispose of. It is also difficult to vary the chemical or mechanical properties across different sections of the surface using traditional lithographic techniques. Moreover, these techniques frequently employ ion-bombardment methods that may damage the substrate. Traditional lithographic techniques are also incapable of processing large surface areas; the largest area that can be fabricated for semiconductor applications is approximately one square inch. To fabricate larger areas, a number of smaller areas must be processed and subsequently fitted together, a costly and time consuming process (c.f. U.S. Pat. No. 5,669,303).
The development of organic self-assembled monolayers (SAM) has addressed some of the problems associated with traditional lithographic techniques. These monolayers can be patterned, enabling the variation of surface properties over a given area (C. S. Dulcey, et al., Langmuir, 12:1638, 1996). Some methods of SAM formation involve the use of bulk solutions of the individual molecules in different solvents. The substrate on which the SAM is to be deposited is immersed in the solution, from which the molecules chemisorb or physisorb onto the substrate surface.
Another recently developed technique, contact printing, combines the advantages of self-assembled monolayers and lithographic techniques. For example, U.S. Pat. Nos. 5,512,131 to Kumar, et al., and 5,900,160 to Whitesides, et al., the entire contents of both of which are incorporated herein by reference, disclose a method of patterning the surface of a material by stamping it with a chemical species that can form a self-assembled monolayer. The surface of the stamp is coated with the chemical species and the stamp placed in contact with a surface to transfer the chemical species from the stamp to the surface, leaving a self-assembled monolayer deposited according to a pattern on the surface of the stamp. The portions of the surface that are not covered by a SAM may be etched, plated, or filled in with an additional SAM-forming species. To form a pattern on a cylindrical surface, the surface may be rolled over a planar stamp. Alternatively, a planar stamp can be used to form a pattern on a large surface by disposing it about a cylinder that is rolled over the surface to be patterned. Examples of the patterning of a cylindrical surface are described in U.S. Pat. No. 5,951,881, to Rogers, et al., the contents of which are incorporated herein by reference.
For procedures in which either the stamp or the stamped surface is rolled, alignment of the stamp with the surface is critical. If a cylindrical substrate is rolled over the stamp, the alignment of the substrate with the stamp must be precisely adjusted to ensure that, if a portion of the substrate is double stamped, then only previously stamped portions of the substrate are double stamped. Otherwise, portions of the surface which were not meant to be stamped may come in contact with the raised features of the stamp, resulting in deposition of material. For a large area stamp, the stamp must also be carefully placed to ensure that any distortion due to gravity does not result in misplacement of the stamp on the surface. A number of methods of ensuring proper alignment and stamp placement are disclosed in U.S. Pat. No. 5,925,259 to Biebuyck, et al., U.S. Pat. No. 5,669,303 to Maracas, et al., and U.S. Pat. No. 5,947,027 to Burgin, et al. Deformation of the stamp is also addressed in U.S. Pat. Nos. 5,937,758 and 5,817,242 to Maracas, et al., U.S. Pat. No. 5,948,621 to Turner, et al., and U.S. Pat. No. 5,725,788 to Maracas, et al. These inventors also describe a number of applications exploiting surfaces patterned with self-assembled monolayers. U.S. Pat. No. 6,013,446 to Maracas, et al., discloses a method and apparatus for placing a biological reagent on a substrate using contact stamping technique. U.S. Pat. No. 5,976,826 to Singhvi, et al., and U.S. Pat. No. 5,776,748 to Singhvi, et al., disclose methods and devices for forming patterned arrangements of cells and other biological materials on a surface separated by cytophobic reagents. U.S. Pat. No. 5,727,977 to Maracas, et al., discloses a method for manufacturing a field-effect device such as a transistor using contact-stamping techniques. U.S. Pat. No. 6,020,047 to Everhart discloses a method of contact printing self-assembled monolayers on metallized thermoplastic films.
There remains a need, however, for the development of methods for the stamping of three-dimensional surfaces, particularly for those methods that result in improved registration and alignment of the stamp and more efficient processing.